This invention relates to a position-controlling system and more particularly to a position-controlling system for a machine tool whose position should be defined with high precision.
A position-controlling system, for example, a numerical control system for a machine tool is supplied with a data on the specified position which should be finally reached by the movable section of the machine tool, and based on said data, periodically calculates a numeral denoting each instructed incremental moving of the movable machine section which is required for said section to reach the specified position. Data on the detected actual position of the movable machine section delivered from a position detector attached to a machine tool is periodically converted to a numeral denoting each actual incremental moving of the movable machine section at said detected position. Therefore, the position detector is required periodically to produce an output indicating a correct data on the current position of the movable machine section. However, the customary phase type position detector presents difficulties in correctly detecting the current position of the movable machine section per prescribed period of time. In contrast, an encoder type position detector also accepted in the past can indeed easily provide a data on the current position of the movable machine section per prescribed period of time, but is far more expensive than the phase type position detector and undesirably has low reliability.